A common and well known type of carrier conveyor system comprises a plurality of work carriers, such as wheeled carriers or skids, which are moved along a predetermined path by a main conveyor underlying and engaging the carriers. As the carriers are moved along, workers commonly perform various work functions on the work carried by the carriers. Thus, for example, workers may apply or work upon portions of an automobile body supported by the carriers. In order to obtain optimum efficiency, the carriers are placed in closely spaced longitudinally spaced relation to one another. In such systems, the carrier can be removed from engagement with the main conveyor as may be required.
With the advent of machines such as robots, it is desirable to be able to perform some work functions on the work by the use of such machines. However, such machines may necessitate interruption of the movement of the work carrier for a predetermined period of time and thus the work carrier must be disengaged from the main conveyor. After the work is performed by the machine, the carrier is re-engaged with the main conveyor. Once again to insure optimum efficiency, the carrier must be removed from engagement with the main conveyor and returned to engagement with the main conveyor quickly without the loss of longitudinal spacing on the main conveyor.
Robotic work stations can be inserted into manned assembly or main conveyors either by making the robot mobile (as a human worker) or by providing sufficient accumulation ahead of and behind the robot to provide for a fixed work station. The second method is often preferable because of the much lower cost and better performance level of the robotic equipment.
An excessively long distance is required to provide work time on a slow moving close job spaced conveyor, as is common in the automotive industry. It is therefore, desirable to provide some intervening means of speeding the flow of product (jobs) without disrupting the normal operation of the conveyor. Such a conveyor device should reduce the space and time required to a practical minimum.
Many methods of high speed castered truck transfer have been devised; however, they all have one or more of the following deficiencies:
The trucks are moved on their own casters at high speed, causing fast deterioration. PA1 High noise level. PA1 A high truck modification cost. PA1 Reciprocating devices which cause lost time and additional motion and wear. PA1 An assortment of auxiliary equipment and numerous controls are required. PA1 Floor pits or a significant conveyor elevation changes are required. The latter usually results in long ramps resulting in wasted plant space. PA1 Relatively high maintenance requirements.
As an example, mechanisms have been heretofore proposed for such transfer of the carriers to and from the work station including mechanical and hydraulic devices for grasping the carrier, transferring it to the work station and returning it to the main conveyor. Such devices have been complex and costly to build and maintain.
Accordingly, among the objectives of the present invention are to provide a conveyor system which will remove a work carrier from engagement with the main conveyor, transfer it to the work station, and return it from the work station to the conveyor in the shortest possible distance while making it possible to maintain a proper supply of carriers in advance of and beyond the work station to insure that the remainder of the system has a carrier at each drive position of the main conveyor; which has a low profile; which is accessible for service; which provides ready access to the work station; which is in the normal path of the conveyor; which is low in in cost; which is modular and can be adapted to various systems; which provides a degree of redundancy to permit operation even if a portion of the system malfunctions; which functions without substantial lifting of the carrier; which requires minimal change in the construction of the main conveyor; which requires minimal change, if any to the work carrier; and/or which can be retrofitted to conventional carrier systems.
This invention directs itself to providing a solution to the requirements for a robotic work station, while avoiding the deficiencies of the other available methods. However, because of its low cost and versatility of arrangement, it has excellent utility for handling a variety of racks, skids or other products. It can be arranged in systems of varying size or used as a single section wherever only high speed transfer is required.
In accordance with the invention, means are provided for disengaging the carriers from the main conveyor in advance of the work station and re-engaging the carriers beyond the work station. A transfer conveyor is positioned such that it receives the carriers as they are disengaged, transfers them as required to the work station, removes them from the work station after the work is performed and returns them to the main conveyor. The transfer conveyor comprises a plurality of transfer assemblies positioned along each side of the path of the carriers from the area where the carriers are disengaged from the conveyor through the work station and to the area where the carriers are re-engaged with the conveyor. Each transfer assembly comprises a plurality of longitudinally spaced wheels mounted with their axes transversely of the path of the carriers and adapted to engage the underside of the carriers. The wheels are driven continuously when it is desired such that the carrier is moved by each transfer assembly to the succeeding transfer assembly or position. The number of transfer assemblies is such that there will be sufficient time at the work station to perform the function desired and at the same time there will always be a carrier ready for re-engagement with the conveyor thereby insuring that there will be a carrier at each longitudinally spaced drive position on the main conveyor in the remainder of the conveyor system.